The invention relates to a sley drive for a power loom and more specifically to a sley drive having a cam driven toggle joint connected between a main frame and the sley support.
In the sley drive described in German Application DE-A No. 2 101 720, the toggle joint is in an outstretched position when the reed beats against the fabric and the toggle joint is linked to the sley support above the pivot point thereof. Due to this arrangement, the complementary cam drive must be provided alongside the sley.
In German Patent DE-C No. 302 114, a shut-down mechanism for a power loom is disclosed where the sley is driven by a foldable crank shaft. The crank shaft is caused to fold by an elbow subject to spring pressure. The pivot point is disposed slightly below the crank shaft center line so that the crank shaft is stable when under pressure. However, it cannot be subjected to tension since the crank shaft would stretch somewhat so that the pivot point and the two end points of the crank shaft would be disposed on one line and the crank lever would be in an unstable position. Therefore, the return motion of the sley in the known shut-down mechanism is effected by the proper weight of the sley. Since for shut-down the pivot point of the crank shaft moves against the elbow, the loom can only be shut down when the sley is moving.
In textile power looms the sley is normally driven directly by way of a crank or other cam drive. In heavier power looms for making technical fabrics, e.g. papermachine fabrics, greater beating force of the reed is required and therefore, the sley is driven in most cases by way of a toggle joint which is driven, in turn, by an eccentric or complementary cam drive. In such a mechanism, the toggle joint is operated in a restrained manner.